1. Field of the Invention
The present invention relates to a writing instrument, and more particularly to a double-chuck mechanical pencil having a tip chuck located at the tip of a tip fitting to hold a lead and a delivery chuck for delivering the lead.
2. Description of the Related Art
A conventional example of a mechanical pencil having two chucks is described in Japanese Utility Model Application Laid-Open No. 4-119435.
Generally, a tip chuck and a delivery chuck of such a mechanical pencil are formed of a metal material. To manufacture the tip and delivery chucks, an approximately cylindrical metal material must be sawed, rubbed, and cut by a cutter to divide the material into a plurality of chuck elements (e.g., two or three), which then are subjected to secondary processing such as burr removal.
Subsequently, the chuck elements of the delivery chuck must be extended outwardly, while the chuck elements of the tip chuck must be subjected to secondary processing such as narrowing because excessively-opened chuck elements cause a lead to fall (e.g., drop-out from the pencil) when the tip chuck is moved forward to release the lead. Thus, manufacturing such a mechanical pencil is labor-intensive and costly.